Storage area networks are used to store data from multiple host computer systems, such as servers. A storage area network includes a network of storage systems that are capable of storing a relatively large amount of data. Examples of storage systems include tape libraries, disk array systems, and other types systems.
A tape library is basically a storage system that includes multiple tape cartridges or cassettes that are selectively accessed (for reading and writing) in response to access requests from computer systems. If a data path in the storage area network between a host computer system and the tape library fails during a data transfer operation, typically the entire data transfer operation fails. As a result, the failed data transfer operation must be restarted from the beginning, which is a time consuming procedure. To restart the data transfer operation, an operator has to manually configure a second data path through the storage area network from the host computer system to the tape library. The operator then manually restarts the failed data transfer operation using the second path. Also, the operator has to reposition the storage medium (tape cartridge or cassette) to the original starting position.
The manual restarting of a data transfer operation is thus both time consuming and labor intensive. Furthermore, a data transfer operation, such as a tape backup operation, is usually performed during a relatively limited time window each day (such as after work hours). Therefore, if a backup operation fails, then an operator has to wait until the next available period (usually a day later) before the backup operation can be restarted. This delay in performing the backup increases the risk that data may be lost due to equipment failure.